Apparatus to sever wire bonded to semiconductor devices



June 10, 1969 F, WLLER ET AL 3,448,910

, APPARATUS TO SEVER WIRE BONDED TO SEMICONDUCTOR DEVICES Filed Sept. 2, 1966 Sheet of 2 FIG. 2

INVENTORS v CHARLES FREDRICK MILLER RAYMOND o. ZENKER ATTORNEYS.

June 10, 1969 ,F ETAL 3,448,910

' APPARATUS To SEVER WIRE BONDED TO SEMICONDUCTOR DEVICES Filed Sept. 2, 1966 7 Sheet 2 of 2 A FIG.4 47

1 Ir. i M

F|G.6 79 a4 INVENTORS" CHARLES FREDRICK MILLER" RAYMOND O. ZENKER United States Patent 3,448,910 APPARATUS TO SEVER WIRE BONDED TO SEMICONDUCTOR DEVICES Charles Fredrick Miller, Anaheim, and Raymond O. Zenker, Whittier, Calif., assignors to Sola Basic Industries, Milwaukee, Wis., a corporation of Wisconsin Filed Sept. 2, 1966, Ser. No. 577,582 Int. Cl. B23k 27/00 US. Cl. 2283 11 Claims ABSTRACT OF THE DISCLOSURE In a semiconductor bonding machine, a hydrogen flame impinges on a thin gold wire to sever the gold wire, which has been bonded to a work piece such as a transistor, whenever an auxiliary fuel pump drives the hydrogen fuel through a burner nozzle to increase the size of the flame. The flame cuts the wire and effects formation of properly sized balls at the ends of the wire. Alternatively, a flame baflle rises to expose the flame and effect severence of the wire. A pair of gripper jaws are also provided to grip and pull away the tail of an attached wire.

This invention relates to a method of and apparatus to sever wire and, more particularly, to the severing of fine gold wire and forming balls on the ends thereof in a ball bonding operation.

In ball bonding, a fine wire, generally of pure gold, ranging in diameter from .0007 to .003, is fed through a vertically movable needle and is formed with a ball on the end of the wire projecting beyond the needle. To connect this wire to a contact element on a semiconductor device, or the like, the needle is moved down to engage the ball and carry it into engagement with the contact surface. By the application of heat and pressure, and in some cases with additional vibrations, the ball is caused to bond to the contact surface. The needle is then raised and the semiconductor device is normally shifted under it to bring the needle into vertical registration with a second contact surface which is to be connected to the first surface by the wire. The needle is then lowered to bring the wire into engagement with the second contact surface and to bond it thereto. At the end of this second bonding operation the needle is again raised and the wire is severed between the second contact surface and the raised needle by melting it in a hydrogen flame which will cut the wire and cause balls to be formed on its ends. The short length, or tail of wire left projecting from the second contact element, is then normally broken off to complete the bonding operation by which the two contact elements are connected.

The formation of the balls on the end of the wire is a very important and critical element of the ball bonding process. It is desired to control the size of the ball to a diameter of two to not more than three times the diameter of the wire. A larger ball frequently cannot be contained within the boundaries of the contact area on the semiconductor element which are extremely small. A ball much smaller than two wire diameters will tend to wedge in the bore of the bonding tool or needle which normally has a diameter of about one and one-half times the wire diameter. Control of the ball size requires a high degree of precision in control of the size and shape of the hydrogen flame and in the alignment of the flame with the wire. Consistent control can be achieved only with a sharply pointed small flame which impinges upon the Wire with an alignment accuracy well within the wire size. Heretofore it was common to sever the wire and form balls in the ends thereof with a moving flame system which passed across the wire at a controlled rate.

Such systems were not entirely satisfactory because of the difficulty of controlling accurately the flame size and rate of movement and because of the congested space in which the severing operation must be effected.

It is, accordingly, one of the objects of the present invention to provide a method and apparatus to sever a wire in which the severing flame is not required to move but is maintained out of contact with the wire during the bonding operation and contacts the wire only during the severing operation.

According to the feature of the invention, the flame is maintained of such small size that even though it is directed toward the wire, it will normally not contact the wire or the needle when the needle is in its lowered position. When it is desired to sever the wire, the size of the flame is temporarily increased in a controlled manner to contact the wire and to melt it and form balls on the ends thereof.

Preferably, fuel such as hydrogen, or hydrogen mixed with alcohol vapor for visibility, is fed to the nozzle at which the flame is produced at a slow rate, normally to produce the small flame. During a severing operation, additional fuel is fed to the nozzle by a pump which stores fuel and increases the supply to the nozzle at a controlled rate and an accurately regulated quantity. In this way, the size of the flame during severing can be accurately controlled to produce the desired severing and ball-forming functions. According to another feature of the invention, the flame is constantly of the desired size for severing the wire and a baflie is moved between the flame and the wire except during the severing operation.

Another object of the invention is to provide a method of and apparatus to sever wire in which the superfluous length of wire, or tail, extending from the last bond is automatically removed in conjunction with the flame cutoff operation.

According to a feature of the invention, the wire is gripped at a point between the last contact area to which it is bonded and the cutoff point so that the wire will be accurately positioned to be contacted by the flame and severed. At the completion of the severing operation, the gripper which grips the wire, is moved away from the semiconductor device to break off the tail of wire extending from the last contact. I

The above and other objects and features of the invention will be more readily apparent from the following description when read in connection with the accompany ing drawings in which:

FIGURE 1 is a partial side view of an apparatus embodying the invention with parts in section;

FIGURE 2 is a partial top view of the apparatus of FIGURE 1;

FIGURE 3 is a partial view similar to FIGURE 1 of an alternative form of apparatus;

FIGURE 4 is a partial view similar to FIGURE 3 showing a modification thereof;

FIGURE 5 is a partial plan view with parts in section of a tailpulling apparatus embodying the invention;

FIGURE 6 is a partial section on the line 6-6 of FIG- URE 5; and

FIGURE 7 is a partial plan view of the gripper jaws of the tail-pulling apparatus.

As shown in FIGURE 1, a Wirebonding machine embodying the invention comprises a housing or framework 10 which supports the several parts of the bonding mechanism. An arm 11 extends through an enlarged opening in the housing 10 and is moved vertically through control means which may be connected to the arm by a rod 12. At its outer end the arm 11 carries a bonding tool or hollow needle 13 through which wire, as indicated at 14, is fed to be bonded to a semiconductor device. The location of a device to which the wire is to be bonded is indicated at 15, and it will be understood that this may be a partially completed header of a transistor, a rectifier, or similar semiconductor device. A machine generally similar to that referred to above is more particularly disclosed in the co-pending application of Miller et al., Serial No. 428,132, filed Jan. 26, 1965, now Patent No. 3,307,761, and owned by the assignee of this application.

According to the present invention, the wire is severed and balls are formed on the severed ends thereof by a hydrogen flame at a point between the last bonding point on the semiconductor device, and the needle when the needle is in its raised position as shown. Fuel for the flame, which is normally pure hydrogen, is supplied from a suitable tank or other source through a conduit 16 to a bubbler device 17 in which alcohol vapor is added to the hydrogen to make the flame visible. The device 17 is more particularly described and claimed in the co-pending application of Miller et al., Serial No. 483,647, filed August 30-, 1965, now Patent No. 3,385,647, and owned by the assignee of this application. From the bubbler device the fuel is fed through a conduit 18 to a check valve 19, which will prevent reverse flow of fuel in the piping system. The check valve 19 is connected through one branch of a T fitting 21 to the lower end of a pump cylinder 22 The T fitting is connected at its other branch to a conduit 23, which is connected to a fixed mounting block 24. The mounting block 24 connects through a fitting 25 to a burner tube 26 which terminates at its end in a small burner nozzle 27 at which the flame is produced. The fitting 25 is preferably universally adjustable and may contain a plastic ferrule 28 so that the burner tube 26 can be adjusted both angularly and rotationally to position the flame accurately. Preferably flats, as shown at 29, are provided in the burner tube to be engaged by a wrench or other suitable tool for turning the burner tube to the desired angle.

The cylinder 22 contains a piston which is movable therein and which is connected to a piston rod 31 extending through the upper end of the piston. A spring 32 normally urges the piston rod and piston upwardly until the upper end of the piston rod abuts against an adjustable stop screw 33. By adjusting the screw 33, the displacement of the piston and the quantity of fuel delivered on each operation of the pump can be accurately controlled. The piston is moved downwardly to force the fuel contained in the cylinder therefrom through the conduit 23 and the burner tube 26 to the burner nozzle to increase the size of the flame. For this purpose, air is supplied to the upper end of the cylinder by a conduit 34 containing a threeway control valve 35, which in one position will supply air under pressure to the upper end of the cylinder to move the piston down against the spring 32 and in another position will vent the upper end of the cylinder to atmosphere so that the spring can raise the piston. As shown in FIG- URE 2, the fuel supply to the conduit 16 is controlled by a needle valve 36 which can be accurately adjusted by a knob 37 to control very accurately the rate of fuel supply from the source. The needle valve 36 is preferably positioned between the hydrogen supply source and bubbler 17, as shown.

In the use of the apparatus as so far described, the burner tube is adjusted to a position in which the flame therefrom, when extended, will impinge precisely upon the length of wire extending between the last bond and the needle 13 in its raised position. The needle valve 36 is then adjusted to regulate the supply of fuel to the burner nozzle to a point where the flame will constitute only a small pilot flame as indicated at 38 in FIGURE 1, which is too small to contact the wire. In order to protect the needle 'from the heat of this small pilot flame when the needle is lowered to effect a bond, a baflie 39 may be connected to the arm 11. When the needle is lowered to effect a bond, the baflie 39 will lie between the needle and the flame nozzle 37 to shield the needle from the pilot flame.

The machine may then be operated by moving the arm 11 downward with a contact positioned beneath the needle to effect a bonding operation. At the completion of the bonding operation, the needle is raised to its elevated position, as shown in FIGURE 1, during which movement Wire pays out through the needle. With the needle in its elevated position, the valve 35 may be opened to supply compressed air to the upper end of the cylinder 22. This will cause the piston in the cylinder to move downwardly against the spring 32 to the end of its full stroke. At this time, the check valve 19 will close and fuel which was in the cylinder 22 will be pumped out through the conduit 23 and the burner tube 26 temporarily to increase the supply of the fuel to the nozzle thereby to increase the flame size. Preferably, the bores in the fitting 21, which are relatively large, are provided with drilled plugs 41 which reduce the volumetric capacity of the connections between the pump and the nozzle.

The nozzle tip 27 is small so that it restricts rapid flow of the gas, resulting in a build up of pressure in the gas supply so that the flame size will increase substantially to the size as shown at 42 in FIGURE 1 in which it projects into contact with the wire. The fuel pressure will build up rapidly as the pump operates so that the flame will extend to its maximum size very rapidly. Also because of the small size of the nozzle, decay of the increased fuel pressure will be relatively slow. Therefore, by adjusting the volumetric capacity of the pump through the adjustable stop 33, the duration of the extended flame can be controlled very accurately to produce precisely the desired severing and ball-forming effects.

At the conclusion of the severing and ball-forming operation, the cylinder 22 may be vented through the valve 35 and the pump piston may be returned to its upper stop position by the combination efiects of the spring 32 and the gas pressure acting on the lower end of the piston. At this time, the check valve is open and gas will flow through the tube 18, check valve 19, and fitting 21 into the pump and also through the conduit 23 to the burner tube to maintain the small pilot flame 38. If necessary, the exhaust of compressed air from the upper end of the cylinder 22 may be throttled to retard the upward piston stroke in order that the pump will not take all of the gas flowing through the valve 36 and thereby extinguish the pilot flame. With the arm 11 and the needle 13 raised and the flame reduced to pilot size which will not impinge upon the wire or the needle, the apparatus is ready for a second bonding operation.

In the embodiment shown in FIGURE 3, parts corresponding to like parts in FIGURE 1 are designated by the same reference numerals. In this construction, the burner tube 26 is positioned in the same manner as in the embodiment of FIGURE 1 to direct its flame accurately toward the wire, but the valve controlling the supply of fuel to the nozzle is adjusted so that the flame will be of maximum size to effect the severing and ball-forming operations at all times. In this construction, as shown, the arm 11 is normally urged to its upper position by a spring 43 and a spring loaded stop 44 is provided to engage the arm and stop movement thereof short of its upper maximum position but in a position in which the needle 13 is raised above its bonding position.

In order to prevent impingement of the flame on the needle and on the length of wire extending between the needle and the contact area, bafiie 45 is provided adapted to project between the flame nozzle 27 and the wire and needle. The baflie 45 is carried at one end of an arm 46 which is pivoted at its end 47. The arm and baffle will tend to drop :by gravity to the position shown in which the baifle deflects the flame away from the needle and wire. A fixed stop block 48 engages the rod 46 and limits downward movement of the rod and baflle to the position shown. In order to move the baffle from the path of the flame, the arm 11 has a downwardly projecting bracket 49, thereon, carrying a pin 51, which extends beneath the arm 46 at a point relatively close to the pivot 47.

In operation of this embodiment of the invention, the parts normally occupy a rest position, as shown in FIG- URE 3. In this position, the arm 46 is resting on the fixed stop 48, and the pin 51 is in contact with or is closely adjacent to the lower surface of the arm 46. When the arm 11 is moved downward to effect a bonding operation, the pin 51 will move away from the arm 46, but the arm 46 and baffle 45 will remain in the position shown in which the flame is directed away from the needle and wire. After completion of a bonding sequence, the arm 11 will be raised by the spring 43 to the illustrated rest position in which the yielding stop 44 engages the arm and stops upward movement thereof.

To effect a severing operation, the controls of the machine, not shown, are operated to overcome the force of the yieldable stop 44 and elevate the arm 11 to its maximum upward position. As the arm moves upward from its rest position, the pin 51 will engage the rod 46 and .move it upward out of the path of the flame. At this time the flame will impinge upon the length of wire extending between the last bond and the needle to sever the wire and form balls on the severed ends thereof.

Due to the fact that the pin 51 engages the rod 46 at a point relatively close to the pivot 47, the rod 46 will be swung upward rapidly to move the baflle 47 a distance substantially greater than the movement of the arm 11. As a result of rapid withdrawal of the baffle from the path of the flame, the flame will impinge upon the wire sharply to effect the severing operation and to produce balls of consistent size on the ends of the wire. It is noted in this connection that if the, baffle were moved upward slowly, the flame would tend to sweep along the wire and could not produce consistent balling.

At the end of the severing operation, which may be accurately controlled in its duration, the machine controls operate to allow the arm 11 to return to its rest position ready for a repetition of the bonding and severing operations.

Instead of relying upon upward movement of the arm 11 from its rest position to remove the baflle from the path of the flame, a separate power device could be provided for this purpose as illustrated in FIGURE 4. In this construction, the bracket 49 and pin 51 are omitted and the fixed stop 48 is replaced by a power device 52, such as an air cylinder or a solenoid. As shown, the device 52 is an air cylinder containing a piston whose piston rod 53 extends from its upper end to engage the rod 46. The piston and piston rod normally occupy a lowered position, as shown, in which the end of the piston rod engages the arm 46 to limit further downward movement, thereof. This position of the rod 46 corresponds to the rest position shown in FIGURE 3.

When it is desired to elevate the rod 46 to .move the bafiie 45 out of the path of the flame, air is supplied to the lower end of the cylinder 52 through a supply conduit 54 to raise the piston and the piston rod. The supply of .air can be controlled to effect the desired upward movement of the rod 46 and bafile and the time interval during which the baffle is removed from the path of the flame can be accurately controlled by suitable control valves or timers or the like.

FIGURES 5 and 6 illustrate a tailpulling attachment which can be used with either of the embodiments of the invention shown in FIGURES l and 2 or FIGURES 3 and 4. The tailpulling attach-ment, as illustrated, comprises a pneumatic cylinder 55, which is rigidly mounted at one end to a slide block 56. The slide block 56 is mounted for sliding movement in a supporting block 57 secured to the frame of the machine. The position of the slide block relative to the adjusting block, is adjustable by a screw 58 threaded into the slide block and having' intermediate its ends a pair of spaced collars 59 which fit on opposite sides of a plate or yoke 61, secured to the supporting block. A lock nut 62 may be threaded on the projecting end of the screw 58 to lock it securely in adjusted position. It will be seen that by loosening the lock nut and turning the screw 58, the slide block 56 will be moved horizontally with respect to the mounting block 57 to adjust the position of the cylinder 55 axially of its length.

The slide block is formed with .a tubular extension 63 which is reduced in diameter adjacent to its outer end and which is threaded as shown. A collar 64 fits over the outer end of the tubular extension 63 and is rotatable thereon to a desired adjusted position. Locking means, not shown, is preferably provided to secure the collar in the desired adjusted position. The collar is held in place on the extension 64 by a nut 65 threaded onto the outer threaded end of the extension 63.

The collar 64 carries a yoke structure 66 projecting outwardly thereon, and in which a Supporting body 67 is pivoted at 68. The supporting body 67, as shown, comprises a lever pivoted at 68, intermediate its ends, and a head 69. An adjustable stop screw 71 carried by one end of the lever is adapted to abut the collar 64 to limit swing of the lever in one direction. Swinging of the lever in the opposite direction is limited by a similar adjustable stop screw 72 threaded in a cross bar 73 on the yoke structure 66.

As best seen in FIGURE 6, the head 69 is formed with a guide track slideably to receive a link 74. A jaw member 75 is also rigidly attached to the head 69 .and extends outward therefrom to terminate in an inwardly turned end 76 informed at its tip with a gripper jaw 77 to grip the wire.

The sliding link 74 is connected to a rod 78 which extends through an enlarged opening in a slideable block 79. The block 79 extends through an elongated slot 81 in the gripper jaw 75 and is secured to a movable jaw 82, which is movable lengthwise of the jaw 75. The jaw 82 has an offset tip portion 83 which is aligned with the tip portion 77 of the gripper jaw 75.

In order to provide a controlled degree of friction to resist relative movement of the jaws and to resist movement of rod 78 through the opening in the slide block 79 a pair of friction springs are provided. As shown, a sinuously bent leaf spring 84 acts between the fixed jaw 75 and the rod 78 to resist relative movement thereof With a relatively light friction. A bowed leaf spring 85 is positioned in the opening through the slide block 79 and bears frictionally against rod 78 with a substantially higher degree of friction than that created by the spring 84.

The sliding link 74 is pivotally connected by a screw 86 or the like to a link 87. The link 87 is in turn pivotally connected through a pivot 88 to a tubular socket member 89 which is secured as by screw threading as shown in FIGURE 5 to the piston rod 91 of a piston slideable in the cylinder 55.

The gripper portions of the jaws 7 6 and 82 are formed as best seen in FIGURE 7 to grip the wire without squeezing it excessively. As shown, the tip 77 of the gripper jaw 75 is recessed at the end, as shown at 92, a depth, approximately 75% of the diameter of the wire being used. This recessing enables the wire to release freely from the jaws when they open, and also prevents the jaws from deforming the wire excessively or cutting it at the point where it is gripped.

The operation of this tail pulley apparatus is controlled through any suitable type of controls, either manual or automatic to function in timed relationship with the remainder of the apparatus. During a bonding operation, the tailpulling mechanism will occupy a position shown in FIGURE 5 in which the jaws are swung away from the path of the wire so that they will not interfere with the wire or with movements of the needle. When a bonding operation has been completed and the wire is ready to be severed, compressed air is fed to the outer end of the cylinder 55 to move its piston to the left as seen in FIG- URE 5. During the initial movement, the rod 78 will be held against movement relative to the jaw 75 by the friction of the spring 84. Thus, a force will be exerted on the guide body 69 which will tend to rock the support assembly 69, 67 about the pivot 68 in a counterclockwise direction, as seen in FIGURE 5. This movement will continue until the adjustable stop 71 engages the collar or yoke 64 at which time further movement will be prevented. By proper adjustment of the stop 71, the jaws will be stopped in a position substantially as shown in FIGURE 7, wherein the wire is relatively close to the jaw tip 77 and is in registration with the recess 92 therein. The positioning of the wire closely adjacent to the jaw 77 is adjusted by the adjusting screw 58 which will move the entire tailpulling mechanism laterally toward and away from the wire.

As the piston rod moves further to the left, the rod 78 will slip on the spring 84- and will move the slide block 79 and the jaw 82 to the left until the wire is gripped between the recessed portion 92 of jaw 77 and jaw 83. Continued movement of the piston rod to the left will simply cause the rod 78 to slide through the slide block 7 9 against the friction of the spring 85.

The jaws are positioned as shown in FIG. 1 at a level between the bonding point and the flange nozzle. Thus, when the wire is gripped by the jaws the position of the wire is accurately fixed in a line between the jaws and the needle at which the flame can impinge accurately upon it.

Upon completion of the wire severing and ball forming operation by the flame, the supply of air under pressure to the cylinder 55 is reversed so that the piston rod 91 will be moved to the right as seen in FIGURE 5. During the initial part of this movement, the support structure 67, 69 will swing clockwise about the pivot 68 until the lever 67 engages the adjustable stop screw 72. By adjusting this screw, the swinging movement of the jaws away from the path of the wire and the needle can be accurately adjusted. During this initial movement, the jaws will remain closed to grip the wire due to the friction produced by the spring 85. Thus, as the jaws pivot to their rest position, they will pull on the short length or tail of wire extending from the last bonding point. This will break the wire adjacent to the last bond at the point of maximum deformation in the wire caused by the bonding tool and the jaws will carry away the short length or tail of wire as they swing to their rest position.

Continued movement of the piston rod 91 to the right will overcome the friction effect of the spring 84 and will shift the movable grip jaw 82 to the right until its end abuts the guide body 69. Further movement of the piston to the right will slide the rod 78 through the slot in the slide block 79 against the friction of the spring 85 until the movable jaw is fully retracted. When the jaws are open in their rest position, they will release the short tail of wire which may easily be picked up by vacuum ,conveying apparatus to carry it out of the machine. It will be seen that with the apparatus as shown the jaws can be accurately adjusted to grip the wire at the. desired elevation. This is accomplished by turning the yoke or collar 64 on the support extension 63 and securing it in properly adjusted position. The screw 58 enables the fixed jaw 77 to be accurately positioned in close proximity to the wire and adjustment to the stop screws 71 and 72 position the jaws to straddle the wire properly preparatory to gripping it and to swing away from the wire to the necessary extent. It will be noted that the tailpulling apparatus can be used with any of the severing embodiments shown or could if desired be used in connection with other types of severing apparatus.

While several embodiments of the invention have been shown and described in detail, it will be understood that these are illustrative only, and are not to be taken as a definition of the scope of the invention, reference being had for this purpose to the appended claims.

What is claimed is:

1. Apparatus to sever wire in a wire bonding machine including a hollow bonding needle through which wire is fed and which is movable linearly between a bonding position at which it bonds the wire to a contact and a retracted position spaced from the contact, said apparatus comprising a nozzle to direct a flame in a fixed direction toward the position of a wire extending from the contact to the needle in the retracted position of the needle, means to maintain the flame out of contact with the needle and the wire While the needle is in its bonding position, said means to maintain including a valve limiting supply of fuel to the nozzle to such an extent that the flame will be too small to contact the needle or the wire, means operative after the needle has moved to its retracted position to cause the flame to contact the wire thereby to sever it and to form balls on its ends, said means operative to cause the flame to contact the wire including a cylinder having a piston movable therein with one end of the cylinder being connected to the fuel supply to the nozzle, means to urge the piston toward the other end of the cylinder and means to supply actuating fluid to the other end of the cylinder to the nozzle.

2. The apparatus of claim 1 including adjustable means to limit travel of the piston thereby to control the quantity of fuel delivered to the nozzle when the piston is moved by the actuating fluid.

3. Apparatus to sever wire in a wire bonding machine including a hollow bonding needle through which wire is fed and which is movable linearly between a bonding position at which it bonds the wire to a contact and a retracted position spaced from the contact, said apparatus comprising a nozzle to direct a flame in a fixed direction toward the position of a wire extending from the contact to the needle in the retracted position of the needle, means to maintain the flame out of contact with the needle and the wire while the needle is in its bonding position, said means to maintain including a baffle movable to a position in front of the nozzle to deflect the flame, and means operative after the needle has moved to its retracted position to cause the flame to contact the wire thereby to sever it and to form balls on its ends, said means for causing the flame to contact the wire including a device engageable with the baflie when the needle is moved away from the contact to move the baflle out of the path of the flame.

4. Apparatus to sever wire in a wire bonding machine including a hollow bonding needle through which wire is fed and which is movable linearly between a bonding position at which it bonds the wire to a contact and a retracted position spaced from the contact, said apparatus comprising a nozzle to direct a flame in a fixed direction toward the position of a Wire extending from the contact to the needle in the retracted position of the needle, mean to maintain the flame out of contact with the needle and the wire while the needle is in its bonding position, said means to maintain comprising a pivoted rod, a baflie carried by the rod and movable to and from a position in front of the nozzle to deflect the flame from the nozzle, and means normally to hold the rod in a position with the battle in front of the nozzle, and means operative after the needle has moved to its retracted position to cause the flame to contact the wire thereby to sever it and to form balls on its ends, said means to cause the flame to contact the wire comprising means engageable with the rod to move it and the baflle to a position in which the baflie is out of the path of the flame.

5. The apparatus of claim 4 in which the last named means is a part movable with the needle and which engages the rod to move it when the needle is moved away from the contact.

6. The apparatus of claim 5 including a yielding stop to stop movement of the needle away from the contact in an intermediate position in which said part has not moved the rod and which will yield to permit further 9 movement of the needle away from the contact during which said part moves the rod.

7. The apparatus of claim 4 in which an expensible fluid actuated device serves in one condition as the means normally to hold the rod in a position with the bathe in front of the nozzle and in another condition serves to move the rod to move the baffle out of the path of the flame.

'8. Apparatus to sever wire in a wire bonding machine including a hollow bonding needle through which wire is fed and which is movable linearly between a bonding position at which it bonds the wire to a contact and retracted position spaced from the contact, said apparatus comprising a nozzle to direct a flame in a fixed direction toward the position of a wire extendingfrom the contact to the needle in the retracted position of the needle, means to maintain the flame out of contact with the needle and the wire while the needle is in its bonding position, means operative after the needle has moved to its retracted position to cause the flame to contact the wire thereby to sever it and to form balls on its ends, a wire gripper between the contact and the nozzle, means to move the gripper into gripping engagement with a wire extending between the contact and the needle in its retracted position, and means operable after severing of the wire to move the gripper away from the contact thereby to break off the length of wire extending from the contact.

9. Apparatus to severe wire in a wire bonding machine including a hollow bonding needle through which wire is fed and which is movable linearly between a bonding position at which it bonds the wire to a contact and a retracted position spaced from the contact, said apparatus comprising a nozzle to direct a flame in a fixed direction toward the position of a wire extending from the contact to the needle in the retracted position of the needle, means to maintain the flame out of contact with the needle and the wire while the needle is in its bonding position, means operative after the needle has moved to its retracted position to cause the flame to contact the wire thereby to sever it and to form balls on its ends, a pair of gripper jaws swingable in a plane between the contact and the nozzle, means to swing the jaws in said plane from a remote position to a position spanning a wire extending from the contact to the needle in its retracted position and then to bring the jaws together into gripping engagement with the wire, and means operable after the wire is severed to move the jaws to the remote position to break off the length of wire extending from the contact and then to open to release the broken off length of wire.

10. Apparatus to sever wire in a wire bonding machine including a hollow needle through which wire is fed and which is movable linearly between a bonding position at which it bonds the wire to a contact and a retracted position spaced from the contact, said apparatus comprising means to sever a wire extending from the contact to the needle in its retracted position intermediate the contact and the needle, a pair of gripper jaws mounted for movement in a plane normal to said wire and between the contact and the severing means, means operable when the needle is moved away from the contact to move the gripper jaws to a position spanning the wire and then to close the jaws into gripping engagement with the wire, and means operable after the wire is severed to move the jaws in said plane to break olf the length of wire extending from the contact and then to open the jaws to release the broken oif length of wire.

11. The apparatus of claim 10 in which one of the jaws is rigidly secured to a guide body and the other jaw is slidable relative to the guide body, means is provided for supporting the guide body -for limited swinging movement, power means is provided to produce lineal reciprocating movement, and the power means is connected to the guide body and the slidable jaw through friction slidable connections, the connection to the slidable jaw providing greater friction than the connection to the guide body so that the guide body will be swung by the power means before the slidable jaw is moved.

References Cited UNITED STATES PATENTS RICHARD H. EANES, JR., Primary Examiner. 

